In the barren reaches of Arctic Siberia, Sergey and Nikita Zimov, a Russian father-and-son team of scientists, are working on geoengineering measures that sound as if they’re ripped from the pages of a Michael Crichton novel: reintroduce a massive, bygone ecosystem to the Eurasian steppe, including mammoths developed from elephant-mammoth DNA hybrids. Their plan is not, however, just for their own amusement – it’s to fight global warming. Placed in context, their idea isn’t nearly as farfetched as it sounds: the massive permafrost covering much of Siberia is in grave danger of melting away. If it does, dormant microbes frozen in the soil would wake and release enormous quantities of carbon into the air, creating a potentially disastrous climate feedback loop. According to the Zimovs, a new, thriving steppe ecosystem teeming with large, roaming herbivores – Pleistocene Park, as they call it – could keep the dangerous carbon insulated in the ground. And those mammoths that have been extinct for millennia? Thanks to the new gene-editing technology CRISPR, they could be just years away. At once a rather curious father-son portrait, and a revealing investigation of the inventive and extraordinary measures needed to fight global warming, Mammoth is the US filmmaker Grant Slater’s video companion piece to an article by Ross Andersen, senior editor at The Atlantic and former Aeon deputy editor.